1. Field of the Invention
The present invention relates to the technical field of wireless transmission and, more particularly, to a Digital Terrestrial Multimedia Broadcasting (DTMB)-based carrier mode detection system and a receiving system having the same.
2. Description of Related Art
In addition to providing a broadcasting program with better picture and sound qualities, the digital television broadcasting can also provide various data services in comparison with the analog television broadcasting.
With the coming digital epoch, the television broadcasting gradually changes from a conventional analog system to a digital system while the mobile communication is developed from analog systems of the first-generation to voice systems of the second-generation and digital multimedia systems of the third-generation. A digital video broadcasting (DVB) system can overcome the problems of poor receiving quality or unstable signal intensity occurred in the current analog systems and caused by the topographies and the obstacles to thereby provide a broadcasting program with better picture and sound qualities. In addition, the spectral efficiency in the DVB system is increased, and the data amount of programs can be broadcasted more in a limited system bandwidth. More importantly, the DVB can provide various additive services derived from the data broadcasting.
The DVB systems currently proposed by certain nations can be divided into multi- and single-carrier modes. The former mostly uses the Orthogonal Frequency Division Multiplexing (OFDM) modulation technique. The receiving and decoding functions of Transmission Parameter Signaling (TPS) especially play an important role in the digital video broadcasting systems.
As an example of the Terrestrial Digital Video Broadcasting (DVB-T) of European standard, the transmission modes include 2 k and 8 k modes. For the 2 k mode, each OFDM symbol includes 2048 subcarriers, but in application only 1705 subcarriers are used and the remaining ones that are close to two sides of the channel are reserved as a guard band. Among the 1705 subcarriers, only 1512 ones are used to transmit the Quadrature Amplitude Modulation (QAM) signals, and the remaining 193 ones are used to transmit the pilot signals. The pilot signals include 17 TPS pilots, 45 continual pilots and 131 scattered pilots.
Similarly, for the 8 k mode, each OFDM symbol includes 8192 subcarriers, but in application only 6817 ones are active. Only 6048 ones among the 6817 subcarriers are active to transmit the QAM signals, and the remaining 769 ones are active to transmit the pilot signals. The pilot signals include 68 TPS pilots, 177 continual pilots and 524 scattered pilots.
The TPS pilots in the DVB-T system transmit the synchronization signal and the transmission-associated parameters such as coding rates (½, ⅔, ¾, ⅚, ⅞), QAM modulation modes (Quadrature Phase Shift Keying (QPSK), 16-QAM, 64-QAM), guard interval lengths (¼ TU, ⅛ TU, 1/16 TU, 1/32 TU), transmission modes (2 k, 8 k), and the like. Accordingly, the receiver can accurately decode the TPS in advance, so as to ensure that the subsequently received data can be accurately decoded.
US Patent Publication No. 2006/0088111 has disclosed the channel state information (CSI) to help decoding the TPS. As shown in the block diagram of FIG. 1, a Viterbi input processor 76 provides the CSI and outputs the CSI to a TPS decoder 66 for decoding. However, it does not disclose how to use the CSI as well as the input signals to optimize TPS decoding function, how to properly and effectively design the system to obtain the best TPS decoding function with the use of an equalizer, and how to determine a carrier mode.
Therefore, it is desirable to provide an improved carrier mode detection system to mitigate and/or obviate the aforementioned problems.